Sodium alkyl naphthalene sulfonates (SANS) are anionic surfactants. They have one or more short alkyl chains (typically butyl or isopropyl) on a naphthalene ring that carries a sulfonate group. The best-known grade is sodium dibutyl naphthalene sulfonate, often sold as “wetting agent BX” or under the old trade name Nekal. Unlike naphthalene sulfonate formaldehyde condensates (NNO, SNF), SANS are small molecules. Their main job is fast wetting and penetration, not long-term dispersion.
How SANS work as a wetting agent
- The alkyl-naphthalene part adsorbs on low-polarity surfaces such as fibres, hydrophobic powders and pigments. The sulfonate stays in the water.
- Adsorption lowers the interfacial tension and displaces trapped air, so water penetrates powders and fabrics faster.
- Wetting gets a powder or fibre into the water. Keeping particles apart afterwards usually needs a polymeric dispersant (NNO, MF, lignosulfonate).
Where SANS are used
| Application | Role | What to test |
|---|---|---|
| Wettable powders and water-dispersible granules | Wetting agent alongside a dispersant | Wettability (CIPAC MT 53.3), suspensibility, foam |
| Textile pretreatment and dyeing | Penetrant in scouring, bleaching and dye baths | Sinking or wetting time on the actual fabric, foam, bath stability |
| Pigment and filler wet-out | Speeds powder incorporation | Grind time, viscosity, flocculation |
| Rubber latex and emulsion polymerisation | Co-surfactant | Coagulum, particle size, foam |
SANS vs related naphthalene products
| Product | Structure | Main function |
|---|---|---|
| SANS / dibutyl naphthalene sulfonate (BX) | Small alkylated monomer | Wetting, penetration |
| Dispersant NNO | Naphthalene sulfonate formaldehyde condensate | Dispersion of dyes and pigments |
| Dispersant MF | Methylnaphthalene sulfonate formaldehyde condensate | Dispersion with high heat stability for disperse and vat dyes |
| SNF superplasticizer | Naphthalene sulfonate formaldehyde condensate, concrete grade | Cement water reduction |
A similar chemical name does not make these interchangeable. A wetting agent will not act as a concrete superplasticizer, and a condensate dispersant is a poor fast wetter.
Buying and qualification
- Confirm the exact alkyl type, active matter and inorganic salt content from the current TDS and SDS.
- Compare grades by wetting time at equal active concentration, in your own water and temperature.
- Check foam; SANS can foam strongly in agitated baths.
Wetting agents for agrochemical, textile and pigment formulation are handled by the group’s surface chemistry division: sodium dibutyl naphthalene sulfonate uses (greenagrochem.net). For industrial dispersants, see Dispersant NNO and Dispersant MF, or contact info@greenagrochem.com.
